What are those boats that don't move on the river?

You may be talking about fairway markings, which are used to divide fairways. It not only provides a deeper area for navigation, but also regulates the navigation order. Waterway beacon (ship) adopts anchor-cable-beacon (that is, fixed ship) structure, anchored at the bottom of the river, and the cable has a certain length. Therefore, no matter whether the water is rising or retreating, the ship is under the current. Generally, there is a lower center of gravity and a longer keel under this ship.